The GSM mobile phone standard includes 112 as an emergency number, and in countries where 112 is not the standard emergency telephone number, GSM telephone users who make calls to 112 generally have their calls redirected to the local emergency telephone number, if it exists. This is valuable for foreign travelers, who may not know the local emergency number. Most GSM mobile phones can dial 112 calls even when the phone keyboard is locked or the phone is without a SIM card.

Using 112 instead of another emergency number on a GSM phone may be advantageous, since 112 is recognized by all GSM phones as an emergency number. A phone dialing a different emergency service's number may refuse to roam onto another network, leading to trouble if there is no access to the home network. Dialing 112 forces the phone to make the call on any network possible. However, some GSM networks (e.g. in Belgium, Spain, UK, Liechtenstein, Austria) are reported to connect emergency calls only from phones with a valid account on their network, e.g. customers and roamers only. [citation needed] Some GSM networks will not accept emergency calls from phones without a SIM card, or even require a SIM card that has credit. Latin American GSM networks typically do not allow 112 calls without a SIM.

Not all countries treat wireless emergency calls in the same way. In general, a country's emergency numbers will all route to 112 as a single point of contact for mobile-originated emergency calls. By contrast, Singapore treats 995 calls for Fire or Ambulance as an emergency call but these calls are not routed to 112. So the phone will dial this number using emergency rules but the call routes to 995 not 112. In Singapore, 112 is only for the Police.

In the United States, the FCC requires networks to route every mobile-phone 911 call to an emergency service call center, including phones that have never had service, or whose service has lapsed. As a result, there are programs that provide donated used mobile phones to victims of domestic violence and others especially likely to need emergency services.

Mobile phones generate additional problems for emergency operators, as many phones will allow emergency numbers to be dialed even while the keypad is locked. Since mobile phones are typically carried in pockets and small bags, the keys can easily be depressed accidentally, leading to unintended calls. A system has been developed in the UK which connects calls where the caller is silent to an automated system, leaving more operators free to handle genuine emergency calls. [2]